1. Technical Field
The invention relates to roofing structures for buildings and more particularly to metal deck roof structures having an overlay of a meltable insulation material. Even more particularly the invention relates to such a roofing structure which seals openings formed at the junctions of the overlapping metal sheets and provides both a thermal and physical barrier preventing the insulation material upon becoming liquid during a fire, from leaking into the building below.
2. Background Information
Roofing systems for commercial and industrial buildings utilize various types of sheet metal panels which are laid in an overlapping relationship and secured to a lower structured frame of a roof deck. An insulation layer is laid on top of the metal sheets which is then covered by a waterproof material, one common type of which is EPDM, together with a ballast or other hold down system. One type of insulation material is a polystyrene foam which is expanded or extruded, usually in sheets, which provide the desired insulating qualities as well as being lightweight thereby contributing very little to the overall weight load of the roof.
However, one problem with the use of such foam insulation in roofing structures is that the foam can melt and burn when the building experiences a fire, and more importantly becomes liquid with the resulting molten liquid flowing through the joints of the roof deck into the building interior below increasing the hazard to occupants as well as to the safety forces during a fire. These metal roof deck sheets are usually fluted with peaks and valleys, with the overlying joint formed between adjacent panels, which usually occurs in a valley, which makes the joint opening very susceptible to the molten liquid flowing through the joint opening and other openings in the steel deck and into the building below. Various systems have been devised to provide an effective seal to metal roof decks, either to prevent the flow of water or other liquid through the joints and panel openings and into the building interior.
U.S. Pat. Nos. 2,106,390 and 2,616,283 disclose roof structures in which the flutes of the metal decks are filled with a granular material. However, this filling material hardens and is used to provide the attachment means for receiving nails or other fasteners for securing the insulation on the top of the metal sheets and not for sealing the overlap joint of adjacent roof deck sheeting.
U.S. Pat. No. 4,936,071 discloses a metal roof wherein the joints are sealed with a tape laminate formed of an unvulcanized EPDM and butyl rubber to provide for a waterproof seal at the overlapping joints.
U.S. Pat. No. 5,392,583 discloses another metal roof installation using flexible elongated elastic strips for sealing the overlapping joints.
U.S. Pat. No. 5,479,753 discloses a metal roof in which an elongated strip of flexible hot melt thermoplastic bituminous composite material is placed over the overlapping joints or seams and heated to bond the strip to the metal roof to provide a weather proof seal therebetween.
U.S. Pat. Nos. 3,763,614 and 4,449,336 disclose other metal roofing structures using various types of barriers between the insulation and the roof deck for reducing the harmful affect should the building experience a fire.
U.S. Pat. No. 4,747,247 discloses a roof system in which the troughs or valleys of the metal sheets are filled with various nonflammable loose packed granular inorganic material which is intended to absorb the molten liquid resulting from the insulation sheets during a fire. However, a major draw back of this type of system is that it adds considerable weight to the building since nearly every trough or valley must be filled with this loose packed granular material. Even if a light weight granular material is used, the weight required to be supported by the underlying roof deck is increased considerably due to the vast amount of material that is required to fill the valleys and troughs in order to absorb the heated liquid material.
U.S. Pat. No. 3,511,007 discloses still another metal roofing structure in which a closed cell non-absorbent foam material is sprayed on the edge of the metal roof sheet, individually or in combination with a breaker strip, for bonding to the undersurface of the adjacent metal sheet edge when it is placed thereon to provide a waterproof seal at the joint formed by the overlapping metal panel edges.
Although these various roof systems achieve certain desired results, in many instances they either materially increase the weight that must be supported by the roof, or are expensive and time consuming to install due to the amount of material required and the labor cost to install the same.
Therefore the need exists for an improved method and roof sealing system which does not materially increase the weight of the roof and which is inexpensive and easy to install, yet provides for the desired fire resistant liquid seal between overlapping joints of adjacent metal panels to prevent the molten liquid formed by the overlying insulation during a fire from flowing into the building below.